1. Field of the Invention
The present invention relates generally to photography, and particularly to means on a camera for indicating unambiguously whether or not the camera is loaded with film.
2. Description of the Prior Art
It has long been known to provide a camera with means for indicating how much film in the camera has been or remains to be exposed. Such means typically are actuated by a camera mechanism that operates in conjunction with movement of a film image area to or from its exposure position in the camera.
For example, U.S. Pat. No. 2,741,168 discloses a 35 mm still-picture camera having a rotatable counter wheel bearing indicia that are sequentially presentable to a viewing window. The periphery of the wheel is provided with ratchet teeth that are engaged by a detent spring to prevent backward rotation of the wheel. The wheel is rotated, or indexed, in its forward direction by a spring-like indexing finger attached to a manually reciprocatable slide member. Also attached to the slide member is a pair of spring-like fingers that are adapted to engage sprocket holes provided along the marginal edge portions of film in the camera to advance succeeding image areas of the film sequentially to and from an exposure position. The slide member is first pulled in a direction outwardly from the camera body to draw the indexing finger away from the counter wheel and to move the film-advancing fingers to a film-engaging position. As the slide member is then pushed back into the camera body, the film-advancing fingers engage an appropriate pair of sprocket holes to advance both the exposed image area out of the exposure position and the next unexposed image area into the exposure position. As the film is so advanced, the indexing finger engages an appropriate one of the ratchet teeth and rotates the counter wheel to a position wherein the next succeeding indicium appears in the viewing window. After all of the film image areas have been exposed, the numeral 0 appears in the window to so advise the user.
The camera body is then detached from the lens-and-shutter assembly and turned over to a processing laboratory for development of the film. A new camera body containing a fresh supply of unexposed film, and displaying the numeral 0 in its viewing window, is then attached to the lens-and-shutter assembly. Thus, while it reasonably can be assumed that film, either exposed or unexposed, is always present in such a camera body when in the possession of the user, there is an ambiguity in this system in that when 0 appears in the window, there is nothing to indicate whether none or all of the film has been exposed.
For another example, U.S. Pat. No. 1,626,606 discloses a camera adapted to receive a film holder containing a plurality of sheet-like film units that are sequentially exposable and transportable from an exposure position in the camera to a processing tank attached to the camera. A rotatable counter wheel bears indicia that are sequentially movable to a viewing site to indicate the number of film units which have been exposed and transported to the processing tank. The counter wheel is rotated, or indexed, from one numerical position to the next by movement of a reciprocatable film-advancing lever to its film-engaging position. During movement of the lever in the opposite, film-advancing direction, the counter wheel is prevented from rotating backward by detent means engaged therewith.
Thus, as in U.S. Pat. No. 2,741,168, the counter wheel rotates unidirectionally from its initial position sequentially through its several numerical positions and thence to its initital position again, whereby the initial position indicates that either none of the film units or all of them have been exposed and transported. Moreover, since there is nothing in the counter mechanism that senses presence or absence of a film holder in the camera, the counter wheel could be in its initial position, or any other position, when there is no film in the camera.
Of more recent vintage is U.S. Pat. No. 3,653,313, which discloses an exposure counter used in a single-lens-reflex type of processing camera. The counter comprises a rotatable wheel having on its periphery a plurality of indicia that are sequentially presented to a viewing window as the wheel is rotated. A serious ambiguity exists in this counter in that when the wheel presents the indicium D to the viewing window, the camera may be in either of two mutually exclusive states: (1) there may be no cartridge in the camera at all, or (2) there may be a fully loaded cartridge, i.e., one having a full complement of (ten) film units with a dark slide covering them, in the camera. Consequently, when the letter D appears, there is no externally visible way of indicating to the user whether or not the camera has a cartridge in it.
The counter wheel is rotated, or indexed, in its counting direction in response to movement of the camera's reflex mirror during each exposure-and-processing cycle. Starting with the camera when fully loaded, the counter wheel is indexed from its letter-D position to its number-1 position during the cycle in which the dark slide is exposed and ejected from the cartridge, then sequentially to its number-2 through number-10 positions during the succeeding cycles in which film units 1 through 9 are exposed and ejected, and finally to its letter-E position during the cycle in which film unit 10 is exposed and ejected, leaving the cartridge empty. When the cartridge is removed from the camera, a return spring rotates the counter wheel back to its empty-camera position, wherein the letter D again appears in the viewing window.
Insertion of a cartridge into the camera causes two things to happen: (1) it allows an indexing pawl coupled to the mirror to be spring-urged into engagement with ratchet teeth on the counter wheel, without moving the wheel, and (2) it allows an anit-backup pawl to be spring-urged into engagement with the ratchet teeth to prevent backward rotation of the wheel. Conversely, removal of the cartridge from the camera causes both the indexing pawl and the anti-backup pawl to be moved out of engagement with the ratchet teeth, thereby freeing the wheel for backward movement by the return spring to its empty-camera position. It will thus be seen that, since the counter wheel does not change position upon insertion of a cartridge, the counter disclosed in this patent suffers from the ambiguity that results from displaying the same indicium in the viewing window when the camera is in two mutually exclusive conditions.
One approach to eliminating such ambiguity is suggested in U.S. Pat. No. 1,583,656. This patent discloses a motion-picture camera having a film-footage indicator that is movable under a viewing window in response to changes in the radius of the film winding on a supply spool inserted into the camera. Changes in film-winding radius are sensed by a movable follower arm that is spring-urged toward the center of the spool. The arm thus moves radially inward between the spool's opposing flanges as the film is unwound. The arm, being coupled to the film-footage indicator, moves the indicator accordingly.
In order to remove the spool from the camera, the follower arm must first be moved radially outward beyond the spool flanges. That is done when a slidable latch member is pulled to unlatch the camera loading door. As the follower arm is thus moved beyond the spool flanges, the film-footage indicator is simultaneously moved to a corresponding position. As long as the latch member remains pulled out, whether any film is in the camera or not, and whether the door is open or closed, the follower arm and indicator will remain so moved, thereby presenting a possible ambiguity to the user. After a new spool of film has been inserted and the door then closed, the latch member must be pushed back in to its fully latched position before the follower arm and indicator can sense and indicate the film footage. Thus the system disclosed in this patent not only poses the possible ambiguity mentioned, but also requires the separate step of manipulating a latch member in order to render the system operative.
The camera devices described in the foregoing paragraphs are exemplary of various means in a camera for indexing a film counter, or indicator, that operate in association with movement of film to or from its exposure position. In all of them, the counter or indicator may present some ambiguity to the user. With particular regard to the matter of positively determining presence or absence of film in a camera, another body of prior art is of interest. Such prior art discloses various camera adjustments that may be made in response to insertion of a film cartridge into the camera.
For example, U.S. Pat. No. 2,043,901 discloses a motion-picture camera having a movable member that senses a coded dimension of a recess or projection on a film magazine inserted into the camera. The sensing member translates the sensed dimension to an adjustable exposure control mechanism to adjust the mechanism in accordance with the film sensitivity represented by the dimension.
Similarly, U.S. Pat. No. 2,493,928 discloses a motion-picture camera having electrical contact means for sensing the length of a conductive strip on a cartridge of film inserted into the camera, the length of the strip being coded in accordance with the film sensitivity, to adjust an exposure control device in the camera.
U.S. Pat. No. 3,025,777 discloses a 35 mm still-picture camera having mechanical means for sensing the locations of two projections on an inserted cartridge, the locations of the projections being coded in accordance with film sensitivity, for the purpose of adjusting an exposure control indicating device in the camera.
Similarly, German Pat. No. 864,803 discloses a 35 mm still-picture camera having a sensing member that is engaged and pivoted by a projection on a cartridge being inserted into the camera. The length of the projection is coded to represent the type and sensitivity of film in the cartridge. Movement of the sensing member is used, via a gear segment and pinion, to rotate an indicating dial in accordance with those film characteristics.
U.S. Pat. No. 2,320,722 discloses a 35 mm still-picture camera having an indicia-bearing member that is movable, in response to insertion of a cartridge into the camera, to a position indicating the type of film in the cartridge. This camera poses the ambiguity that the same indicium is displayed when a cartridge containing "normal" film is in the camera as when no cartridge is in the camera.
U.S. Pat. No. 3,110,215 discloses various embodiments of an invention usable in motion-picture cameras. The invention relates to magazine orientation indicators for cameras adapted to use reversible film magazines, particularly such indicators capable of showing whether a reversible magazine has been inserted into a camera in its first-side or second-side orientation. The invention comprises coding means on the first and second sides of the magazine, to distinguish one side from the other, and a code sensing member in the camera that is movable, in response to insertion of the magazine, by an amount proportional to the coding means.
In one embodiment, the sensing member bears indicia indicating whether an inserted cartridge is in its first-side or second-side orientation, or whether there is no cartridge in the camera at all. While this embodiment thus eliminates the aforementioned ambiguity regarding presence or absence of film in the camera, its indicator is in no way connected to, or associated with, the camera's film-footage indicator, but instead constitutes a second indicating device built into the camera, thereby increasing the complexity and cost of the camera and requiring the user to observe two indicators.
In an alternative embodiment, a rotatable code sensing member adapted to sense first-side or second-side orientation of an inserted magazine is coupled to an indicating arm that cooperates with the film-footage indicator dial. When the magazine is inserted in its second-side orientation, the sensing member and indicating arm are rotated to a position wherein an indicium on the arm indicating second-side orientation is presented to a viewing window. During such rotation, the indicating arm rotates the film-footage indicator dial by an incremental amount to compensate for the shorter length of leader attached to what initially was the film supply spool but now is the film take-up spool. Thus the user an definitely can when an inserted magazine is in its second-side orientation. However, the same ambiguity referred to above in connection with other prior-art cameras exists in this embodiment, in that the code sensing member, the indicating arm, and the film-footage indicator dial all occupy the same respective positions under two mutually exclusive camera conditions: (1) when a magazine is in the camera in its first-side orientation, and (2) when there is no magazine in the camera at all. Hence, this patent fails to resolve the problem of eliminating such ambiguity without resorting to a second indicating device in the camera.
Finally, U.S. Pat. No. 3,485,157 discloses a 35mm still-picture camera adapted to receive film cartridges having a projection whose location is coded to represent the number of exposures provided for on the strip of film in the cartridge. The camera has a code sensing member which is movable, in response to insertion of a cartridge into the camera, by an amount proportional to the coded location of the projection. Movement of the code sensing member causes an exposure indicator dial to be rotated to a position that presents to a viewing window the number of exposures available in the cartridge. While this device is helpful in indicating the length of film supplied by a coded cartridge inserted into the camera, there still exists serious ambiguity of the type referred to above. Thus, when the number 36 appears in the window, any one of the following three conditions may prevail: (1) there may be a 36-exposure cartridge in the camera, (2) there may be an uncoded cartridge in the camera, or (3) there may be no cartridge in the camera.
It is well known, of course, to provide a camera with a viewing window through which the user can view backing paper attached to film loaded into the camera. The film may simply be roll film, e.g., size-127 film, supplied on a spool which is inserted into the camera; or it may be film supplied in a cartridge, e.g., a size-126 cartridge, having a viewing window that becomes aligned with the camera window when the cartridge is inserted into the camera. In either case, the user can tell at a glance whether there is film in the camera or not, and how much of the film has been or remains to be exposed. Such information is readily provided by indicia printed on the film backing paper and viewed through the viewing window(s). While this well-known expedient leaves no room for ambiguity, it obviously is feasible only with film having backing paper or other opaque covering material adapted to prevent fogging of the film through the viewing window(s). Some widely used films, e.g., 35mm films and integral self-processable film units, typically are supplied in cartridges without such backing material. For such films, an indicating device in the camera is highly desirable.
A review of all the prior art discussed in the foregoing paragraphs indicates a long-felt but unresolved need for a simple, reliable, and convenient device in a photographic camera that indicates precisely and exclusively, i.e., without ambiguity, the true state or condition of the camera, relative to film used therein, at any particular time; a device that operates automatically, i.e., without requiring any special manipulation by the user to render it operative; a device that does not rely on film covering material to do the indicating; a device that does not require a special indicator in addition to a film-exposure or film-footage indicator already provided on the apparatus.